pragma solidity ^0.4.16;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, throws on overflow.
  */
  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
    // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    c = a * b;
    assert(c / a == b);
    return c;
  }

  /**
  * @dev Integer division of two numbers, truncating the quotient.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    // uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return a / b;
  }

  /**
  * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  /**
  * @dev Adds two numbers, throws on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}

/******************************************/
/*       ITECToken STARTS HERE       */
/******************************************/
contract ITECToken {

    // Public variables of the token(TokenERC20)
    string public name;
    string public symbol;
    uint256 public totalSupply;
    uint8 public decimals = 18; // 18 decimals is the strongly suggested default, avoid changing it

    address public owner;
    
    using SafeMath for uint; // use the library for uint type

    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    constructor(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol
    ) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
    
        owner = msg.sender;
    }
    
    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    mapping (address => bool) public frozenAccount;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
    event FrozenFunds(address target, bool frozen);
    
    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);
    
    //authorized parts start
    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) onlyOwner public {
        owner = newOwner;
    }
    //authorized parts end
    
    /* Internal transfer, only can be called by this contract */
    function _transfer(address _from, address _to, uint _value) internal {
        require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require (balanceOf[_from] >= _value);               // Check if the sender has enough
        require (balanceOf[_to] + _value >= balanceOf[_to]); // Check for overflows
        require(!frozenAccount[_from]);                     // Check if sender is frozen
        require(!frozenAccount[_to]);                       // Check if recipient is frozen
        
        balanceOf[_from] = balanceOf[_from].sub(_value);                         // Subtract from the sender
        balanceOf[_to] = balanceOf[_to].add(_value);                           // Add the same to the recipient

        emit Transfer(_from, _to, _value);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public returns (bool success) {
        _transfer(msg.sender, _to, _value);
        return true;
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` in behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        
        allowance[_from][msg.sender] = allowance[_from][msg.sender].sub(_value);

        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) onlyOwner public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        
        balanceOf[msg.sender] = balanceOf[msg.sender].sub(_value);            // Subtract from the sender
        totalSupply = totalSupply.sub(_value);                      // Updates totalSupply

        emit Burn(msg.sender, _value);
        return true;
    }

    /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
    /// @param target Address to be frozen
    /// @param freeze either to freeze it or not
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        emit FrozenFunds(target, freeze);
    }
}